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Wednesday, February 26, 2014

The American Midwest is in the grip of yet another polar vortex, a long dip southward of the jet stream that carries cold arctic air into the region. At least we had a stretch of moderate weather between the last vortex and this one, enough to melt most of the snow and clear the roads. This being February, this cold snap is not nearly as bad as the last one, but it is much colder than average and the ground is frozen solid.

The beginning of plant growth, what we think of as Spring, will obviously be set back several weeks. The spinach I planted last October that overwintered inside the plastic greenhouse is showing a little growth. Usually by this time it would be larger, but whenever the weather breaks it should grow quickly. At least the soil inside the greenhouse is no longer frozen.

The schedule for starting seeds was pushed back about two weeks. A few weeks ago I assembled the seedling rack. Since I had a set of casters stored in the minibarn that were taking up space it seemed like they might as well go on the legs of the rack as this thing when loaded is heavy and hard to move.

The top and bottom shelves are fastened in place with screws while the two middle shelves can be moved to any number of positions. I had some leftover Reflectix insulation from the cold frame project and attached that to the back side of the unit. This will reflect some light back onto the plants. The light unit has four 32W T8 lamps. Two of the lamps are GroLux bulbs (which look purple) and the other two are 8000K bulbs. This light setup gave very good results last year - thick bushy seedlings.

For my take on lights and plant growth here is the link to an earlier post.

I seeded some lettuce about ten days ago. Last week I seeded two flats of Ruby Ring onions, and two days ago I seeded the first set of brassicas - broccoli, kohlrabi, cabbage and tatsoi. When ready they will go into the plastic greenhouse. After the onions germinate and the weather moderates (it was 6 F this morning) I'll put the onions into the mobile coldframe. That will clear space for more seedlings. The growing season is getting underway, slow but sure.

Friday, February 21, 2014

Last winter I built a wheeled greenhouse/coldframe/potting
bench hybrid.My goal was to build a mobile
cold frame with the performance of a greenhouse.Empty, it should be
light enough for one person to move.It
also had to be well insulated and with some stone or water inside able to
maintain temperatures above freezing for one or two cold sunless days.It performed well enough to keep the inside above freezing for at least one day following a sunny day, although last spring there were often several consecutive cold and cloudy days. This picture shows the unit with the door
propped open.There’s an earthbox inside and a block of stone
to absorb and store solar heat.The
little box held a remote temperature sensor.

This is what the greenhouse looked like
in the back yard last March.The glazing
is made from twin-walled polycarbonate.Commonly used in greenhouses in place of glass, it is very transparent,
lightweight,nearly unbreakable, and
with two walls has insulating properties similar to insulated glass.

The greenhouse was built from concept as a prototype.It’s like trying to pull an idea out of thin
air and then turn it into something made of real materials – you never know
quite where it is going or how it will get there, you just have to sense the
right path and follow it.The end
product had some flaws, for sure, although overall I was pleased with its
performance. and I hoped to sort them
out after the first season.

I found that its biggest flaw was it’s height. At about 6 feet high it was just too tall.It wanted
to tip over when I moved it, and there was always a concern that a strong gust
could blow it over.Here’s another view
of the greenhouse from the backside when I was building it.It’s height not only affected its
functionality, it just didn’t LOOK right. You could put a billboard on that backside.

That high peak needed to be cut down to size,
and that’s what I did.After removing
the door and the siding that was in the way the top was cut down and reframed,
then the siding was put back on.

The hinged front panel was now too large, as you
can see in this picture where the sides of the panel frame now extend about a
foot beyond the opening.I re-attached
the door panel (minus the bottom piece) in order to accurately mark the sides for cutting.The polycarbonate panels also had to be cut
again to fit in the smaller frame.

The glazing was re-installed.There was a scrap piece of styrofoam handy so I cut a piece to fit into the ceiling of
the greenhouse.The more insulation the
better, and the peak is where the heat goes.

Here’s a close up of the glazing on the ends.The sides of the glazing slide into grooves
while the top and bottom is fastened with screws with rubber washers.The top is fastened on the inside of the
frame while the bottom is attached on the outside of the frame.That strategy ensures that water will always
be shed to the outside.

The cedar 1”x8” boards were reattached to the
sides.They hide the screw heads and
since there is a gap between the lites and the boards they provide a nice
handhold for moving the unit.

I stapled Reflectix insulation to the back and beneath the bench floor.This material is like silvered bubble
wrap.It not only adds R-value to the
unit but will reflect light back onto the plants.

Brackets were installed to hold a wood bar
across the back wall.I plan to set
concrete paving blocks on the bench floor as well as stand them on end along
the back wall.The wood bar will hold
the blocks in place.The more thermal
mass to store solar heat the longer the greenhouse will hold heat on cloudy
days.

The greenhouse looks mostly finished but one of
the most challenging problems was still ahead.Designinga closure and lock
system for the doors of a small structure can be as difficult as designing the
structure itself.The old props held the
door panel only at the fully open position,I wanted something that would open the door to a number of positions,
from open just a bit to all the way up. This is what the old prop set up looked
like, adapted to the newly modified unit.

I found that on warm sunny days the greenhouse
would quickly overheat with the door panel shut.Last year I jerry-rigged some pieces of wood inside the
greenhouse to prop it open slightly and let the heat escape. I wanted a functional fix that would hold the door open at different angles and yet fit neatly
and unobtrusively into the structure.Easier
thought than done, I tried numerous approaches, none of which worked like I
wanted.Finally I came up with this.As simple as this system looks, it took hours
of experimentation with different arm lengths and pivot points to find this
setup.Here’s the door panel propped
fully open.

Here’s the panel propped at the first détente.By golly it’s just about finished. After several warm days the snow is nearly
gone, and once the ground is firm I will
wheel the greenhouse into the backyard and set the paving stones inside.Onions and lettuce have been seeded in the
house.When they are ready they will go
into the greenhouse.It looks like the
new season is underway.

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About this Blog

I moved to this place in SW Indiana in 2008. The property is six acres of woods, pasture, yard and pond. Usable garden space with full sun is limited by surrounding trees to 250 square feet of raised beds, more the size of an urban garden. I use intensive techniques: rotation of plant families, nutrient cycling, cages and trellises, row cover and cold frames to get the most out of the space.

About Me

A native Hoosier, I worked in the construction trades and later in life got a chemistry degree and worked in a research lab until retirement. I raise vegetables because they taste better and it saves money. What other hobby pays for itself? I'm a cheapskate - I won't buy new seeds until the old ones aren't any good. I'm also a bit of a lazy gardener - if I can buy the seedlings I want then why start the seeds, or if I can engineer a way to make it less work I'll do so. I also drink too much beer. But I never (well almost never) work in the garden and drink beer.